1. Field of the Invention
This invention relates to casting machines and more particularly to an automatically controlled casting machine of the type which produces metal casts, as for example dental casts.
2. Description of the Prior Art
Casting machines are used for the casting of perfect metal casts, as is needed in various fields of technology, such as dentistry. Such casting machines are presently available, as for example, the Chronomatic System I Casting Machine marketed by the Whaledent International Co., N.Y., N.Y. Such casting machines contain a casting chamber which can support an alloy filled, open-ended container and an investment casting ring having a sprue hole. The sprue hole is positioned above the open end of the container. The casting chamber contains a handle which is manually manipulated. While held in an initial upright position, a vacuum is introduced into the casting chamber. After a while the casting chamber is manually inverted permitting the alloy to flow into the mold in the investment ring. Simultaneously, the vacuum is terminated and instead compressed air is allowed to flow into the casting chamber. The casting chamber is maintained in its inverted position, and after a while, is again manually returned to its initial upright position while being vented to the atmosphere.
However, the prior art machine is extremely sensitive to errors and poor casts have been formed. For example, an extremely critical step is the turning of the casting chamber. If the chamber is turned too slowly, an incomplete cast is formed. If the casting chamber is turned too abruptly, the alloy will be spilled. If the venting takes place too quickly, the upper button of the sprue hole will be broken off and the sprue will be hollow. Additionally, if the setting time under pressure is too short or the setting time under compressed air is improper, the cast will also be faulty and of improper shape. Also, an incomplete casting can occur if the vacuum is too weak, the pressure too low, or the solidification time too short. A short solidification time will also cause shrinkage in the casting resulting in holes near the sprue entrance.
Because of the critical timing for the turning of the casting chamber as well as the criticality of the vacuum and pressure time intervals, the numerous imperfections and faults in the resulting casts have made the process an extremely expensive one and frequently requires numerous recasts to produce the final high quality cast needed.